Too bad the kind of people who give polygraphs to root out and fire the gay people in their company don't give a shit about the science (or lack thereof) of polygraph tests.
Well, polygraphs, while not providing undeniable proofs, give statistically significant results. U.S. govt agencies use them widely as part of security clearance.
http://skeptics.stackexchange.com/questions/225/do-polygraph...
http://en.wikipedia.org/wiki/Polygraph